Perovskite halides (e.g., CH3NH3PbI3 or MAPbI3) represent a new class of light absorbers that have demonstrated exceptional, unparalleled progress in solar cell performance from 3.8% in 2009 to a certified 17.9% in 2014. Since then, perovskites have attracted increasing worldwide attention for a variety of optoelectronic fields, including solar cells, light-emitting diodes, and laser applications. However, the standard perovskite MAPbI3 is found to have potential stability issues in moisture-containing environments, especially at elevated temperatures with exposure to light. Thus, improved perovskite halide films are needed for these materials to provide technically and economically viable solar cell alternatives to the current incumbent technologies such as silicon solar cells.